Sorry. I'm not gonna take that blank assertion for granted. A sedentary lifestyle leads to a slower metabolic rate. More muscle mass burns more calories, even at rest, even while asleep. Lance Armstrong consumes more calories in a day than I do. And his left leg burns more of them in an hour than my whole body does in a day.
Well, some folks are simply unable to exercise much due to disability, but by eating less and drinking lots of water (no caffeine or alcohol), it can be proven that the old excuse of slow metabolism can be overcome.
Discipline WORKS!